Reliability and Bifurcation in Neurons Driven by Multiple Sinusoids

We investigated the effect of the phase relationship between two frequency components of a periodic stimulus on cortical neurons and on simulated Integrate- and-Fire (IF) model neurons. It is well established that entrainment to a resonant frequency in a fluctuating stimulus can induce reliable and precise spike trains. Recently, Makeig (Science, 2002) demonstrated stimulus-evoked phase-resetting of rhythms in human EEG. We find that varying the phase between two stimulus sinusoids in the -range (5 and 10 Hz), while holding their power constant, modulated the reliability and precision of a neuron's response. The neuron's output was maximally precise for one phase and maximally imprecise for another. This phenomenon may be understood as a bifurcation between spike-time attractors, which we investigated with IF simulations. Our results suggest phase resetting could switch neurons dynamically between temporal and rate coding